package JVM;

import java.io.IOException;
import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.Method;
import java.nio.file.Files;
import java.nio.file.Path;
import java.nio.file.Paths;

import java.io.ByteArrayOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.net.URL;
import java.nio.file.Files;
import java.nio.file.Path;
import java.nio.file.Paths;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;

public class CustomClassLoader extends ClassLoader {
    private String source;

    // 构造函数，传入类加载来源
    public CustomClassLoader(String source) {
        this.source = source;
    }

    @Override
    protected Class<?> findClass(String name) throws ClassNotFoundException {
        byte[] classData = loadClassData(name);
        if (classData == null) {
            throw new ClassNotFoundException();
        } else {
            return defineClass(name, classData, 0, classData.length);
        }
    }

    private byte[] loadClassData(String className) {
        switch (source) {
            case "filesystem":
                // 从文件系统加载类
                return loadClassDataFromFileSystem(className);
            case "network":
                // 从网络加载类
                return loadClassDataFromNetwork(className);
            case "database":
                // 从数据库加载类
                return loadClassDataFromDatabase(className);
            default:
                // 其他来源
                return null;
        }
    }

    private byte[] loadClassDataFromFileSystem(String className) {
        // 实现从文件系统加载类的字节码数据的逻辑
        String fileName = className.replace('.', '/') + ".class";
        try {
            Path path = Paths.get("path/to/your/classes", fileName); // 替换为实际的文件路径
            return Files.readAllBytes(path);
        } catch (IOException e) {
            e.printStackTrace();
        }
        return null;
    }

    private byte[] loadClassDataFromNetwork(String className) {
        // 实现从网络加载类的字节码数据的逻辑
        try {
            URL url = new URL("http://example.com/classes/" + className.replace('.', '/') + ".class"); // 替换为实际的网络地址
            try (InputStream inputStream = url.openStream(); ByteArrayOutputStream outputStream = new ByteArrayOutputStream()) {
                byte[] buffer = new byte[1024];
                int bytesRead;
                while ((bytesRead = inputStream.read(buffer)) != -1) {
                    outputStream.write(buffer, 0, bytesRead);
                }
                return outputStream.toByteArray();
            }
        } catch (IOException e) {
            e.printStackTrace();
        }
        return null;
    }

    private byte[] loadClassDataFromDatabase(String className) {
        // 实现从数据库加载类的字节码数据的逻辑
        Connection connection = null;
        try {
            // 连接数据库
            connection = DriverManager.getConnection("jdbc:mysql://localhost:3306/test", "root", "huangzhihui@11"); // 替换为实际的数据库连接信息
            String query = "SELECT class_data FROM classes WHERE class_name = ?";
            try (PreparedStatement statement = connection.prepareStatement(query)) {
                statement.setString(1, className);
                try (ResultSet resultSet = statement.executeQuery()) {
                    if (resultSet.next()) {
                        return resultSet.getBytes("class_data");
                    }
                }
            }
        } catch (SQLException e) {
            e.printStackTrace();
        } finally {
            if (connection != null) {
                try {
                    connection.close();
                } catch (SQLException e) {
                    e.printStackTrace();
                }
            }
        }
        return null;
    }

    public static void main(String[] args) {
        // 指定加载类的来源
        String source = "database"; // 可以是 "filesystem", "network", "database" 等
        CustomClassLoader classLoader = new CustomClassLoader(source);

        try {
            // 加载类
            Class<?> clazz = classLoader.loadClass("com.example.MyClass");
            // 创建实例
            Object instance = clazz.newInstance();
            // 调用实例方法
            // ...
        } catch (ClassNotFoundException | InstantiationException | IllegalAccessException e) {
            e.printStackTrace();
        }
    }
}
